Wireless links between a base station and a mobile device will experience fluctuation on a regular basis due to impairments in the channel. These impairments are introduced by motion, localized interference from other transmitters (in-band and out-of-band) and also external factors like terrain, weather, buildings and lack of line of sight etc. To provide the best end-user experience, cognitive radios may need to handoff to a different base station or access point in order to maintain the best link. In multi-channel systems, for e.g. xMax networks, a handoff may involve switching to a different channel (logical or frequency). Therefore, efficiently identifying this new channel is of paramount importance in order to maintain the best link with minimal downtime.
When the device is mobile and moving at vehicular speeds, the link to the current base station or access point deteriorates at a much more rapid pace than when stationary or at pedestrian speeds. Therefore it is even more imperative to reduce the latency involved in identifying such potential channels by the process of proactive scanning.
Cognitive radios strive to maintain the best wireless link with the peer device or base station so as to provide the best end user experience. When the application data stream requires limited bandwidth but for extended periods of time, then the traditional approach of “scanning when idle” does not work.
What's proposed in this disclosure is a novel approach to minimize the amount of time required to identify potential channels and also a scheduling algorithm that will maximize the opportunities for a mobile device to scan for potential channels while continuing to receive send and receive data on the current channel efficiently.
In reference to prior art disclosure US 2011/0116358 A9 this disclosure is novel because Applicant's disclosure is mainly focused on assigning bandwidth around the position of the beacon frame, which is again staggered across channels, while in the above referenced document the beacon is inserted randomly as strip symbols according to certain criteria based upon a characteristic of the cell, or drift, or some means for identifying the subband position for the beacon signal. Applicant's solution is different because the TDD system described has the beacon at known positions staggered across channels purely to facilitate scanning other channels for handoff to. Applicant also primarily describes a scheduling algorithm by the base station that increases the opportunities for the mobile device to scan for other channels.